Communication Apparatus and Communication Method

1. A communication apparatus configured to control a bandwidth of communication when a transmitting apparatus and a receiving apparatus perform communication via a network, comprising: a measuring unit configured to measure the bandwidth for communication of at least one direction of two directions, a first direction from the transmitting apparatus to the receiving apparatus and a second direction from the receiving apparatus to the transmitting apparatus, the measuring of bandwidth by observing at the communication apparatus (i) for the first direction an accumulated data length of a series of first packets sent from the transmitting apparatus, and/or (ii) for the second direction counting the increment of a number indicated by a series of second packets, each second packet sent by the receiving apparatus back to the transmitting apparatus to confirm receipt of a corresponding first packet; a storing unit configured to store information regarding bandwidth adjustment including a target bandwidth indicating a bandwidth required for communication; an adjusting unit configured to read out, from the storing unit, the target bandwidth of the direction for which the bandwidth was measured, and based on a comparison of the bandwidth measured at the measuring unit and the read out target bandwidth, to perform throttling or enhancing of the bandwidth by controlling the transmission interval of the first and/or second packets when relaying or transmitting the first and/or second packets, or duplicates thereof, from the communication apparatus.

2. The communication apparatus according to claim 1 , wherein the adjusting unit is configured to perform throttling or enhancing of the bandwidth by extending or shortening the transmission interval of the second packets respectively.

3. The communication apparatus according to claim 2 , wherein the number indicated by each second packet indicates the first packet that the transmitting apparatus should transmit next; and the adjusting unit is configured to perform throttling or enhancing of the bandwidth by controlling the transmission interval of the second packet so that the increment in the number becomes closer to the target bandwidth.

4. The communication apparatus according to claim 1 , further comprising a packet storing unit configured to store a first packet of the series of first packets and a second packet of the series of second packets, according to information included in the first and second packets indicating an order of the packet; wherein the adjusting unit is configured to compare, upon receiving a packet via the network, the information indicating an order of the packet of the received packet and the information indicating an order of the packet of a packet stored in the packet storing unit; and when the information indicating an order of the packet match each other, discards one of either the packet stored in the packet storing unit or the received packet, and stores the other packet in the packet storing unit.

5. The communication apparatus according to claim 4 , wherein the adjusting unit is configured to duplicate the packet stored in the packet storing unit when the bandwidth in a transmission direction of the first or the second packet is below the target bandwidth for the communication direction, and transmits the duplicate packet at a transmission interval based on the target bandwidth at least once.

6. The communication apparatus according to claim 5 , wherein when the second packet is not recognized for more than a predetermined period, the adjusting unit obtains from the packet storing unit, the first packet whose number indicating an order of the first packet corresponds to the largest number among numbers indicating an order of the second packet, and transmits a duplicate packet of the obtained first packet to the receiving apparatus.

7. The communication apparatus according to claim 5 , wherein when the first packet is not recognized for more than a predetermined period, the adjusting unit obtains from the packet storing unit, the second packet whose number indicating an order of the second packet is the largest number, and transmits a duplicate packet of the obtained second packet to the transmitting apparatus.

8. The communication apparatus according to claim 5 , wherein the adjusting unit improves the transmitting bandwidth at the transmitting apparatus by transmitting duplicate packets continuously more than a predetermined number of times for the second packets having a same number indicating an order of the packet.

9. The communication apparatus according to claim 1 , wherein the measuring unit and the adjusting unit has a first measuring unit and a first adjusting unit configured to perform bandwidth measurement and bandwidth adjustment, respectively, for one of the first and second communication directions between the transmitting apparatus and the receiving apparatus, and a second measuring unit and a second adjusting unit configured to perform bandwidth measurement and bandwidth adjustment, respectively, for the other of the first and second communication directions; and by running the measuring unit and the adjusting unit to perform bandwidth adjustment in the direction of the two communication directions in which a packet is recognized.

10. The communication apparatus according to claim 4 , wherein among the second packets received from the receiving apparatus, the adjusting unit does not send a packet that is to be discarded in the transmitting apparatus, and discards the packet in the apparatus itself.

11. The communication apparatus according to claim 1 , further comprising a managing unit configured to perform registration of information to the storing unit with reception of a packet from the transmitting apparatus and the receiving apparatus as a trigger, and starts management of a session between the transmitting apparatus and a receiving apparatus; wherein the storing unit stores information regarding bandwidth adjustment for the session, associating with information identifying the session between the transmitting apparatus and the receiving apparatus.

12. The communication apparatus according to claim 11 , wherein the session managing unit refers to information included in the packet representing a state transition of communication, and if a value indicating termination of the session between the transmitting apparatus and the receiving apparatus is stored in the information representing the state transition, eliminates the information identifying the session and the associated information regarding bandwidth adjustment from the storing unit, and generates and transmits, to the transmitting apparatus or the receiving apparatus being a transmission destination of the packet, a notification packet notifying termination of communication.

13. The communication apparatus according to claim 11 , wherein when the session managing unit has not recognized a packet related to a session that is being managed for more than a predetermined period, the session managing unit eliminates the information identifying the session and the associated information regarding bandwidth adjustment from the storing unit, and generates and transmits, to the transmitting apparatus and the receiving apparatus, a packet notifying termination of communication.

14. The communication apparatus according to claim 1 , comprising: wherein the adjusting unit sets, for the packet for which bandwidth adjustment has been performed, information indicating that a bandwidth adjusting process has already been performed, and based on whether or not the information is set for a received packet, determines whether or not the received packet is subject to bandwidth adjustment.

15. The communication apparatus according to claim 14 , wherein the adjusting unit sets 0 in an URGENT bit of a TCP (transmission Control Protocol) header of the packet, sets information indicating that a bandwidth adjusting process has already been performed in an URGENT pointer field, and sets a value including a value of the set information in a checksum field of the packet.

16. The communication apparatus according to claim 1 , wherein the measuring unit compares the measured bandwidth and the target bandwidth, and if the measured bandwidth exceeds the target bandwidth, increases the target bandwidth within an allowable range of the target bandwidth set in advance, and if the measured bandwidth is below the target bandwidth, reduces the target bandwidth within the allowable range, and stores the changed target bandwidth in the storing unit.

17. The communication apparatus according to claim 11 , wherein the managing unit changes the target bandwidth of a session being managed based on a range of a network address of a packet, a type of a communication protocol, a duration of communication, time period, the measured bandwidth or a transmitted data amount, and stores the changed target bandwidth in the storing unit.

18. A communication method to control a bandwidth of communication when a transmitting apparatus and a receiving apparatus perform communication via a network, comprising: measuring the bandwidth for communication of at least one direction of two directions, a first direction from the transmitting apparatus to the receiving apparatus and a second direction from the receiving apparatus to the transmitting apparatus, the measuring of bandwidth by observing at the communication apparatus (i) for the first direction an accumulated data length of a series of first packets sent from the transmitting apparatus, and/or (ii) for the second direction counting the increment of a number indicated by a series of second packets, each second packet sent by the receiving apparatus back to the transmitting apparatus to confirm receipt of a corresponding first packet; and reading out, from a storing unit configured to store information regarding bandwidth adjustment including a target bandwidth indicating a bandwidth required for communication, the target bandwidth of the direction for which the bandwidth was measured, and based on a comparison of the bandwidth measured at the measuring unit and the read out target bandwidth, to perform throttling or enhancing of the bandwidth by controlling the transmission interval of the first and/or second packets when relaying or transmitting the first and/or second packets, or duplicates thereof, from the communication apparatus.

19. The communication method according to claim 18 , further comprising: setting, for the packet for which bandwidth adjustment has been performed, information indicating that a bandwidth adjusting process has already been performed, and based on whether or not the information is set for a received packet, determining whether or not the received packet is subject to bandwidth adjustment.